1. Field of the Invention
The present invention pertains to drill pipe safety valves used for capping oil field drill pipe when a blowout occurs through the pipe. More particularly, the present invention provides a mechanism for positioning the safety valve over the drill pipe and for altering the device for use on various drill pipe and thread patterns.
2. Related Art
When during the drilling of an oil well the bit penetrates an earth formation having an unexpectedly high pressure, the hydrostatic head of the drill mud standing in the well may not be sufficient to prevent formation fluids from entering the bore hole and traveling upward toward the surface. If such flow is not controlled quickly, a "blowout" of the well can occur and create very serious safety hazards of personnel working on and around the drilling rig. Of course a resulting fire can cause tremendous damage to the drilling equipment. At first indication of possible blowout conditions, the blowout preventers can be closed a round the drill pipe to seal off the annulus. If the kelly by which the drill pipe is driven happens to be attached to the upper end of the string of drill pipe, a valve may be present in the system which can be closed to shut off upward flow through the drill pipe itself. However, should upward flow begin while the kelly is not connected to the drill pipe, for example while a threaded connection between pipe sections is being made, a very hazardous situation is presented.
U.S. Pat. No. 4,026,354, issued May 31, 1977, shows a somewhat massive device that is lowered over the open end of the pipe by a crane or a boom and operated by a long drive shaft that extends through a kill line in order to make a connection with the pipe and enable a shut-off valve to be closed. Due to its massive nature, this device could not be positioned and put into operation as quickly as would obviously be desirable under the circumstances. U.S. Pat. No. 3,625,282, issued Dec. 7, 1971, shows a device having a clamp that mates only with a special type of groove arrangement on the upper end of the casing, the clamp having bolt holes that can be aligned with matching holes on the lower flange of a spool which mounts a master valve. The clamp and spool have an offset hinge bolt to enable the spool to be pivoted into position. However this apparatus requires the makeup of numerous bolts before complete attachment can be accomplished, which is time-consuming and thus potentially dangerous, and the clamp assembly is designed for attachment only to a specific type of machined end fitting.
Applicant is the inventor of the invention claimed in U.S. Pat. No. 4,442,892, issued Apr. 17, 1984, which patent is expressly incorporated herein by reference for all purposes, and which shows an apparatus for stabbing and threading a safety valve into a well pipe. The apparatus comprises a tubular canister rotatably mounted on a carriage assembly that is slidably mounted on an upstanding frame. The lower end of the frame has a swivel mounting to a bracket that is attached to the side of an elevator-type clamp means by which the apparatus is clamped onto the upper end portion of the pipe. With the canister pivoted into position over the pipe, a gear drive is operated by a hand wheel to cause the canister to be rotated and simultaneously lowered toward the pipe whereby a safety valve mounted inside the canister is automatically threaded ino the upper end of the pipe and can be closed to shut off upward flow.
It is a general object of the present invention to provide a mechanism to facilitate operation of an apparatus such as that described in U.S. Pat. No. 4,442,892 by providing a means for controllably positioning the safety valve over a drill pipe of variable diameter and providing an adjustment in the rotation and lowering of the safety valve dependent upon the type of drilling equipment involved.